Thanks Richard, but approaching it from the other direction does not work in this case. It works fine for our Sonos equipment which can read the iTune Library.xml file, but it does not work for JRiver Media Center which can only import traditional m3u playlists.
Richard & tt2: What is the point of iTunes letting you generate m3u playlists if they are no use to anyone? My problem with the m3u files iTunes generates now is that they contain file references NOT to the actual music in its proper location, but to iTunes itself. Here is an example of such a m3u:
#EXTM3U
#EXTINF:78,Introduction - Dave Brubeck
/Users/XXXXXXX/Music/iTunes/iTunes Media/Jazz/Dave Brubeck/1967 Bravo! Brubeck!/01 Dave Brubeck - Introduction.m4a
#EXTINF:300,Cielito Lindo - Dave Brubeck
/Users/XXXXXXX/Music/iTunes/iTunes Media/Jazz/Dave Brubeck/1967 Bravo! Brubeck!/02 Dave Brubeck - Cielito Lindo.m4a
#EXTINF:375,La Paloma Azul (The Blue Dove) - Dave Brubeck
/Users/XXXXXXX/Music/iTunes/iTunes Media/Jazz/Dave Brubeck/1967 Bravo! Brubeck!/03 Dave Brubeck - La Paloma Azul (The Blue Dove).m4a
The XML playlist is no different:
<key>56464</key>
<dict>
<key>Album</key>
<string>Bravo! Brubeck!</string>
<key>Album Artist</key>
<string>Dave Brubeck</string>
<key>Artist</key>
<string>Dave Brubeck</string>
<key>Artwork Count</key>
<integer>1</integer>
<key>Bit Rate</key>
<integer>662</integer>
<key>Comments</key>
<string>Recorded live in Mexico, May 12-14 1967</string>
<key>Date Added</key>
<date>2017-06-12T14:01:16Z</date>
<key>Date Modified</key>
<date>2017-03-29T13:16:04Z</date>
<key>File Folder Count</key>
<integer>-1</integer>
<key>Genre</key>
<string>Jazz - Cool</string>
<key>Grouping</key>
<string>Cool/West Coast Jazz/Jazz Instrument/Piano Jazz</string>
<key>Kind</key>
<string>Apple Lossless audio file</string>
<key>Library Folder Count</key>
<integer>-1</integer>
<key>Location</key>
<string>file:///Users/XXXXXXXX/Music/iTunes/iTunes%20Media/Jazz/Dave%20Brubeck/ 1967%20Bravo!%20Brubeck!/01%20Dave%20Brubeck%20-%20Introduction.m4a</string>
<key>Name</key>
<string>Introduction</string>
<key>Persistent ID</key>
The problem is that there is no such music in "iTunes Media". All my music resides on a NAS and iTunes has no problem playing this music. The real path to my music is (in OSX):
/volume1/music/Jazz/Dave Brubeck/1967 Bravo! Brubeck!/03 Dave Brubeck - La Paloma Azul (The Blue Dove).m4a